The present invention, in some embodiments thereof, relates to compositions comprising collagen and platelet rich plasma (PRP) for tissue regeneration and, more particularly, but not exclusively, for soft tissue regeneration.
Platelet-rich plasma (PRP) is blood plasma that has been enriched with platelets. As a concentrated source of autologous platelets, PRP contains (and releases through degranulation) several different growth factors and other cytokines that stimulate healing of bone and soft tissue.
PRP functions as a tissue sealant and drug delivery system, with the platelets initiating wound repair by releasing locally acting growth factors via α-granules degranulation. The secretory proteins contained in the α-granules of platelets include platelet-derived growth factor (PDGF-AA, BB, and AB isomers), transforming growth factor-β (TGF-β), platelet factor 4 (PF4), interleukin-1 (IL-1), platelet-derived angiogenesis factor (PDAF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), platelet-derived endothelial growth factor (PDEGF), epithelial cell growth factor (ECGF), insulin-like growth factor (IGF), osteocalcin (Oc), osteonectin (On), fibrinogen (Ff), vitronectin (Vn), fibronectin (Fn), and thrombospondin-1 (TSP-1). These growth factors aid healing by attracting un-differentiated cells in the newly formed matrix and triggering cell division. PRP may suppress cytokine release and limit inflammation, interacting with macrophages to improve tissue healing and regeneration, promote new capillary growth, and accelerate epithelialization in chronic wounds.
Platelets in PRP also play a role in host defense mechanism at the wound site by producing signaling proteins that attract macrophages; PRP also may contain a small number of leukocytes that synthesize interleukins as part of a non-specific immune response.
The delivery and residence of PRP into the injury site remains a challenge due to its liquid state and therefore the potential loss of material to the surrounding tissues. Thrombin (mainly bovine-derived) is a common platelet activator that is used for clot formation and increases the gelation of PRP. The use of thrombin has several disadvantages. Thrombin has undesirable immune response in humans. In addition, in-vitro studies have shown inhibition of cell proliferation and viability (Lawson J H. Semin Thromb Hemost, 2006; 32 (Suppl 1) 98-110; Murray M M et al., J Orthop Res. 2007 35(1) p. 81-91).
Type I collagen, which has a native involvement in the intrinsic clotting cascade, is found to be an attractive alternative to thrombin for platelet activation. Besides being the major protein component in mammalian connective tissue, it is the most studied natural scaffold for regenerative medicine and tissue engineering.
Several in-vitro studies investigated the cytokine release from PRP clots activated by thrombin or by collagen in order to characterize their release profile (Tsay R C, et al., J Oral Maxillofac Surg, 2005 63 p. 521-528; Fufa D, et al., J Oral Maxillofac Surg, 2008 66(4) p. 684-690). Type I collagen in various physical states, soluble or fibrillar, was shown to be as effective as thrombin in stimulating release of TGF, PDGF and VEGF over several days. Cultures of activated PRP either by thrombin or type I collagen were incubated for up to 15 days and collagen-based clot was shown to maintain its initial shape and size where the majority of thrombin based clot was degraded.
Laci et al., Yale J Biol Med. 2010 March; 83(1): 1-9 teaches that calcium chloride may be used to activate PRP clots.
U.S. Patent Application No. 20120201897 teaches the combination of calcium chloride and type I collagen for the activation of PRP clots.